Substituent Effects on the Structures of Silver Complexes with

Inorg. Chem. 2007, 46, 6529−6534

Substituent Effects on the Structures of Silver Complexes with Monoazatrithia-12-Crown-4 Ethers Bearing Substituted Aromatic Rings Yoichi Habata,*,†,‡ Kanae Noto,† and Futoshi Osaka† Department of Chemistry, Faculty of Science, Toho UniVersity, Funabashi, Chiba 274-8510, Japan, and Research Center for Materials with Integrated Properties, Toho UniVersity, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan Received March 21, 2007

New 4′-methoxybenzyl-, 4′-methylbenzyl-, benzyl-, 3′,5′-difluorobenzyl-, 3′,5′-dichlorobenzyl-, and 4′-nitrobenzylarmed monoazatrithia-12-crown-4 ethers were prepared by the reductive amination of monoazatrithia-12-crown-4 with the appropriate benzenecarbaldehyde in the presence of NaBH(OAc)3. Cold electrospray ionization mass spectrometry and X-ray crystallography show that silver complexes with armed monoazatrithia-12-crown-4 ethers bearing aromatic side arms with electron-donating groups or electron-withdrawing groups are coordination polymers and trimers, respectively. The structures of the silver complexes were strongly dependent on the strength of the CH‚‚‚π interactions, which are controlled by substituent effects on the aromatic side arms.

Introduction Many kinds of sulfur-containing macrocyclic ligands such as thia-,1a oxathia-,1b and azathiacrown ethers1c have been prepared in order to develop new ligands with specific binding properties for transition-metal ions. During our research efforts on the development of new armed azacrown and azathiacrown ethers, we reported that a diazahexathia24-crown-8 ether bearing the 3′,5′-dichlorobenzyl group as * To whom correspondence should be addressed. E-mail: habata@ chem.sci.toho-u.ac.jp. † Department of Chemistry, Faculty of Science. ‡ Research Center for Materials with Integrated Properties. (1) (a) Katritzky, A. R., Rees, C. W., Scriven, E. F. V., Eds. ComprehensiVe Heterocyclic Chemistry II; Elsevier: Oxford, U.K., 1995; Vol. 9, Chapter 30. Edema, J. J. H.; Buter, J.; Kellogg, R. M. Tetrahedron 1994, 50, 2095. Blake, A. J.; Li, W.; Lippolis, V.; Schro¨der, M. Chem. Commun. 1997, 1943. Blake, A. J.; Devillanova, F. A.; Garau, A.; Gilvy, L. M.; Gould, R. O.; Isaia, F.; Lippolis, V.; Parsons, S.; Radek, C.; Schro¨der, M. J. Chem. Soc., Dalton Trans. 1998, 2037. Blake, A. J.; Li, W.; Lippolis, V.; Taylor, A.; Schro¨der, M. J. Chem. Soc., Dalton Trans. 1998, 2931. Blake, A. J.; Fenske, D.; Li, W.; Lippolis, V.; Schro¨der, M. J. Chem. Soc., Dalton Trans. 1998, 3961. Blake, A. J.; Devillanova, F. A.; Garau, A.; Isaia, F.; Lippolis, V.; Parsons, S.; Schroder, M. J. Chem. Soc., Dalton Trans. 1999, 525. (b) Katritzky, A. R., Rees, C. W., Scriven, E. F. V., Eds. ComprehensiVe Heterocyclic Chemistry II; Elsevier: Oxford, U.K., 1995; Vol. 9, Chapter 32. (c) van de Water, L. G. A.; Hoonte, F.; Driessen, W. L.; Reedijk, J.; Sherrington, D. C. Inorg. Chim. Acta 2000, 303, 77. Tanaka, M.; Nakamura, M.; Ikeda, T.; Ikeda, K.; Ando, H.; Shibutani, Y.; Yajima, S.; Kimura, K. J. Org. Chem. 2001, 66, 7008. Love, J. B.; Vere, J. M.; Glenny, M. W.; Blake, A. J.; Schro¨der, M. Chem. Commun. 2001, 2678. Tanaka, M.; Ikeda, T.; Xu, Q.; Ando, H.; Shibutani, Y.; Nakamura, M.; Sakamoto, H.; Yajima, S.; Kimura, K. J. Org. Chem. 2002, 67, 2223. Caltagirone, C.; Bencini, A.; Demartin, F.; Devillanova, F. A.; Garau, A.; Isaia, F.; Lippolis, V.; Mariani, P.; Papke, U.; Tei, L.; Verani, G. Dalton Trans. 2003, 901.

10.1021/ic700538f CCC: $37.00 Published on Web 07/13/2007

© 2007 American Chemical Society

side arms incorporated two Ag+ ions in the crown ring, and the aromatic side arms enclosed the Ag+ ions.2 On the other hand, two phenylethyl-appended diazahexathia-24-crown-8 ethers formed a polymer, and the aromatic side arms do not participate in coordination in the solid state. These results indicate that the aromatic side arm plays a key part in the binding of Ag+ ions and substituent effects of the aromatic side arms may affect the structures of the silver complexes. Recently, increasing attention has been focused on the significance of CH‚‚‚π interaction in supramolecular structures and organic reactions.3 Although the CH‚‚‚π interaction is a weak interaction, significant effects on the overall structure are possible when the interaction occurs in polymeric systems. Here we report that the structures of silver complexes with the aromatic armed monoazatrithia-12crown-4 (2a-2f) are changed drastically by CH‚‚‚π interactions, which are controlled by the substituent effect on the aromatic side arms. Experimental Section Melting points were obtained with a Mel-Temp capillary apparatus and were not corrected. Fast atom bombardment mass spectrometry (FAB-MS) spectra were obtained using a JEOL 600 H mass spectrometer. 1H NMR spectra were measured in CDCl3 on a JEOL ECP400 (400 MHz) spectrometer. Cold electrospray ionization mass spectrometry (ESI-MS) spectra were recorded on (2) Habata, Y.; Seo, J.; Otawa, S.; Osaka, F.; Noto, K.; Lee, S. S. Dalton Trans. 2006, 2202. (3) (a) Nishio, M. CrystEngComm 2004, 6, 130. (b) Nishio, M. Tetrahedron 2005, 61, 6923.

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Habata et al. Table 1. Crystal Data and Refinement Parameters for Complexes 2a-AgPF6, 2b-AgOTf, 2c-AgOTf, 2d-AgOTf, 2e-AgOTf, and 2f-AgOTf compound formula M T/K cryst syst space group a/Å b/Å c/Å R/deg β/deg γ/deg U/Å3 Z Dc/g cm-3 µ/mm-1 reflns collecd unique reflns, Rint RFa RF, Rw(F 2) (all data)a compound formula M T/K cryst syst space group a/Å b/Å c/Å R/deg β/deg γ/deg U/Å3 Z Dc/g cm-3 µ/mm-1 reflns collecd unique reflns, Rint RFa RF, Rw(F 2) (all data)a compound formula M T/K cryst syst space group a/Å b/Å c/Å R/deg β/deg γ/deg U/Å3 Z Dc/g cm-3 µ/mm-1 reflns collecd unique reflns, Rint RFa RF, Rw(F 2) (all data)a a

2a-AgPF6 C18H28N2OS3F6PAg 637.44 90 orthorhombic P2(1)2(1)2(1) 8.7234(6) 14.5024(11) 20.6747(16)

2b-AgOTf C19H28N2O3S4F3Ag 625.54 298 monoclinic P2(1)/c 13.8910(8) 9.0832(5) 23.7127(10) 122.378(2)

2615.6(3) 4 1.619 1.127 19 031 3655, 0.0398 0.0332 [3450, I > 2σ(I)] 0.0361, 0.0896

2526.8(2) 4 1.644 1.174 18 228 6255, 0.0555 0.0438 [4173, I > 2σ(I)] 0.0688, 0.0947

2c-AgOTf C36H52N4O6S8F6Ag2 1223.04 298 monoclinic P2(1)/c 24.854(2) 8.9828(9) 23.438(2)

2d-AgOTf C19H27NO4S4F5Ag 664.53 90 orthorhombic P2(1)2(1)2(1) 9.5868(6) 11.6802(7) 22.3982(14)

109.941(2) 78.20(2) 4 1.651 1.204 13 360 8998, 0.0359 0.0442 [4775, I > 2σ(I)] 0.0915, 0.0966 2e-AgOTf C50H73N3O12S12Cl6F9Ag3 2000.14 100 triclinic P1h 8.7183(4) 21.1087(10) 22.2440(10) 72.1060(10) 82.9840(10) 83.0890(10) 3851.5(3) 2 1.725 1.364 29003 18920, 0.0271 0.0567 [14 771, I > 2σ(I)] 0.0752, 0.1619

2508.1(3) 4 1.760 1.201 18 807 3532, 0.0311 0.0312 [3421, I > 2σ(I)] 0.0322, 0.0744 2f-AgOTf C56H72N10O15S12F9Ag3 2004.57 298 trigonal R3h 20.7184(7) 20.7184(7) 32.921(2) 120 12238.2(11) 6 1.632 1.103 28775 6238, 0.0479 0.0758 [4515, I > 2σ(I)] 0.0949, 0.2461

RF ) ∑||Fo - Fc||/∑|Fo|. Rw(F 2) ) [∑w|Fo2 - Fc2|2/∑w]Fo4)]1/2.

a JEOL JMS-T100CS mass spectrometer. 1,4,7-Trithia-10-azacyclododecane (monoazatrithia-12-crown-4, 1) was prepared as previously reported.2 Preparation of Armed Monoazatrithia-12-crown-4 Ethers. N-(4′-Methoxybenzyl)-1,4,7-trithia-10-azacyclododecane (2a).

6530 Inorganic Chemistry, Vol. 46, No. 16, 2007

After a mixture of 4-methoxybenzaldehyde (2.0 mmol) and 1 (1.0 mmol) in dry 1,2-dichloroethane (25 mL) was stirred at room temperature for 1 day under an argon atmosphere (1 MPa), triacetoxysodium borohydride (2.0 mmol) was added, and the mixture was stirred for a further 1 day at room temperature. Saturated aqueous Na2CO3 was added, and the aqueous layer was extracted with chloroform (20 mL × 3). The combined organic layer was washed with water, dried over Na2SO4, and concentrated. The residual oil was recrystallized from hexane to give 2a in 40% yield. Mp: 124-125 °C. 1H NMR (CDCl3): δ 7.24 (d, J ) 8.8 Hz, 2H), 6.85 (d, J ) 8.8 Hz, 2H), 3.78 (s, 3H), 3.57 (s, 2H), 2.79 (s, 8H), 2.73 (t, J ) 7.73 Hz, 4H), 2.63 (t, J ) 7.73 Hz, 4H). FABMS (matrix: m-NBA): m/z 344 ([M + 1]+, 100%). Anal. Calcd for C16H25NOS3: C, 55.93; H, 7.33; N, 4.08. Found: C, 55.51; H, 7.18; N, 3.96. N-(4′-Methylbenzyl)-1,4,7-trithia-10-azacyclododecane (2b). The preparation procedure was the same as that used for 2a. Yield: 43%. Mp: 85.0-86.0 °C. 1H NMR (CDCl3): δ 7.20 (d, J ) 7.78 Hz, 2H), 7.12 (d, J ) 7.78 Hz, 2H), 3.61 (s, 2H), 2.742.81 (m, 12H), 2.63 (t, J ) 7.21 Hz, 4H), 2.34 (s, 3H). FAB-MS (matrix: m-NBA): m/z 328 ([M + 1]+, 20%). Anal. Calcd for C16H25NS3: C, 58.66; H, 7.69; N, 4.28. Found: C, 58.49; H, 7.67; N, 3.88. N-Benzyl-1,4,7-trithia-10-azacyclododecane (2c). The preparation procedure was the same as that used for 2a. Yield: 21%. Mp: 106-107 °C. 1H NMR (CD2Cl2): δ 7.20-7.29 (m, 5H), 3.65 (s, 2H), 2.82 (s, 8H), 2.78 (t, J ) 7.6 Hz, 4H), 2.64 (t, J ) 7.6 Hz, 4H). FAB-MS (matrix: 1:1 DTT/TG): m/z 314 ([M + 1]+, 100%). Anal. Calcd for C15H23NS3: C, 57.46; H, 7.39; N, 4.47. Found: C, 57.42; H, 7.34; N, 4.16. N-(3′,5′-Difluorobenzyl)-1,4,7-trithia-10-azacyclododecane (2d). The preparation procedure was the same as that used for 2a. Yield: 20%. Mp: 88.5-89.3 °C. 1H NMR (CD2Cl2): δ 6.94 (dd, J1 ) 2.0 Hz, J2 ) 8.4 Hz, 2H), 6.71 (tt, J1 ) 2.8 Hz, J2 ) 8.7 Hz, 1H), 3.62 (s, 2H), 2.67 (t, J ) 6.4 Hz, 4H). FAB-MS (matrix: m-NBA): m/z 350 ([M + 1]+, 100%). Anal. Calcd for C15H21F2NS3‚1/4H2O: C, 50.89; H, 6.12; N, 3.96. Found: C, 50.78; H, 6.34. N-(3′,5′-Dichlorobenzyl)-1,4,7-trithia-10-azacyclododecane (2e). The preparation procedure was the same as that used for 2a. Yield: 29%. Mp: 115.0-115.5 °C. 1H NMR (CD2Cl2): δ 7.302 (s, 2H), 7.268 (s, 1H), 3.587 (s, 2H), 2.813 (s, 8H), 2.746 (t, J ) 6.78 Hz, 4H), 2.645 (t, J ) 7.18 Hz, 4H). FAB-MS (matrix: m-NBA): m/z 383 ([M + 1]+, 84%). Anal. Calcd for C15H21Cl2NS3: C, 47.11; H, 5.53; N, 3.66. Found: C, 47.07; H, 5.50; N, 3.56. N-(4′-Nitrobenzyl)-1,4,7-trithia-10-azacyclododecane (2f). The preparation procedure was the same as that used for 2a. Yield: 40%. Mp: 126-128 °C. 1H NMR (CD2Cl2): δ 8.20 (d, J ) 8.8 Hz, 2H), 7.55 (d, J ) 8.8 Hz, 2H), 3.73 (s, 2H), 2.84 (s, 8H), 2.77 (t, J ) 4.8 Hz, 4H), 2.64 (t, J ) 4.8 Hz, 4H). FAB-MS (matrix: m-NBA): m/z 359 ([M + 1]+, 30%). Anal. Calcd for C15H22N2O2S3: C, 50.25; H, 6.18; N, 7.81. Found: C, 50.15; H, 6.14; N, 7.91. Preparation of Silver Complexes. AgOTf or AgPF6 (0.03 mmol) in methanol (1 mL) was treated with the 2 host (0.01 mmol) in acetonitrile (1 mL). Crystals of the corresponding silver complex were obtained quantitatively upon evaporation of the solvent. 2a-AgPF6. Mp: >160 °C (dec). Anal. Calcd for C16H25NOS3AgPF6‚CH3OH: C, 32.49; H, 4.65; N, 2.23. Found: C, 32.81; H, 4.20; N, 2.06.

SilWer Complexes with Monoazatrithia-12-Crown-4 Ethers Table 2. Normalized Cold ESI-MS Intensities of Fragment Ion Peaks of Silver Complexes (L ) Ligand, S ) Solvent, and A ) Anion)

substituents [L + Ag]+ [2L + 2Ag + S]+ [2L + 2Ag + A]+ [3L + 3Ag + A + S]+ [3L + 3Ag + 2A]+ [4L + 4Ag + 2A + S]+ [4L + 4Ag + 3A]+ [4L + 5Ag + 4A]+ [4L + 6Ag + 5A]+ [5L + 5Ag + 4A]+ [5L + 6Ag + 5A]+ [6L + 6Ag + 5A]+ [7L + 7Ag + 6A]+

2a + AgOTf

2a + AgPF6

2b + AgOTf

2c + AgOTf

2d + AgOTf

2e + AgOTf

2f + AgOTf

CH3O 100.0 16.6 5.9 0.9 1.1 0.5 0.5

CH3O 100.0

CH3 100.0

H 100.0

F 100.0

4.8

20.5

11.0

13.7

Cl 100.0 3.1 3.6

NO2 100.0 7.2 8.5

0.8

6.1

1.5

2.1

0.8

0.6

0.7 0.4 0.2

4.5

1.1

0.9

3.0

1.0

0.4

1.9 1.6

0.6 0.3

0.2

2b-AgOTf. Mp: >185 °C (dec). Anal. Calcd for C17H25NO3S4F3Ag‚1/2CH3CN: C, 35.73; H, 4.41; N, 3.47. Found: C, 35.63; H, 4.52; N, 3.49. 2c-AgOTf. Mp: >177 °C (dec). Anal. Calcd for C16H23NO3S4F3Ag‚3/4H2O: C, 33.69; H, 4.06; N, 2.46. Found: C, 32.91; H, 4.23; N, 2.40. 2d-AgOTf. Mp: >165 °C (dec). Anal. Calcd for C16H21NO3S4Ag‚CH3CN: C, 33.39; H, 3.74; N, 4.33. Found: C, 33.30; H, 3.81; N, 3.95. Single crystals for X-ray analysis were obtained by further recrystallization from acetone. 2e-AgOTf. Mp: >120 °C (dec). Anal. Calcd for C16H21NO3S4Cl2F3Ag‚1/2H2O: C, 29.64; H, 3.42; N, 2.16. Found: C, 29.67; H, 3.48; N, 1.76. 2f-AgOTf. Mp: >115 °C (dec). Anal. Calcd for C16H22N2O5S4F3Ag‚CH3OH: C, 31.53; H, 4.05; N, 4.33. Found: C, 31.75; H, 3.72; N, 4.09. X-ray Structure Determination. Crystals of AgOTf or AgPF6 complexes with 2a-2e were mounted on the tip of a glass fiber, and data collection was carried out on a Bruker SMART diffractometer equipped with a CCD area detector at 90-298 K. The data were corrected for Lorentz and polarization effects, and absorption corrections were applied with the SADABS4 program. The structures were solved by direct methods and subsequent difference Fourier syntheses using the program SHELX.5 All non-H atoms were refined anisotropically, and H atoms were placed in calculated positions and thereafter refined with Uiso(H) ) 1.2Ueq(C). The crystallographic refinement parameters of 2a-AgPF6, 2b-AgOTf, 2cAgOTf, 2d-AgOTf, 2e-AgOTf, and 2f-AgOTf are summarized in Table 1, while selected bond distances and angles and close CH‚ ‚‚π distances of these complexes are listed in Tables 3 and 4, respectively. Calculation of the Electrostatic Potential Isosurfaces. Density functional theory (DFT) calculations (B3LYP/6-31G*)6 using 6-31G* as an initial geometry were performed using Spartan 047 computer modeling software. The isosurface values of the substituted benzene derivatives are displayed at 8.1 electrons/au.3

Table 3. Selected Bond Distances (Å) and Angles (deg)

Results and Discussion

Table 4. Close CH‚‚‚Benzene Plane Distances (Å)

New armed monoazatrithia-12-crown-4 ethers bearing substituted aromatic ring pendants were prepared by the (4) Sheldrick, G. M. SADABS, Program for absorption correction of area detector frames; Bruker AXS, Inc.: Madison, WI, 1996. (5) SHELXTL, version 5.1; Bruker AXS, Inc.: Madison, WI, 1997. (6) Stephens, P. J.; Devlin, F. J.; Chabalowski, C. F.; Frisch, M. J. J. Phys. Chem. 1994, 98, 11623. Rauhut, G.; Pulay, P. J. Am. Chem. Soc. 1995, 117, 4167. Rauhut, G.; Pulay, P. J. J. Phys. Chem. 1995, 99, 3093. (7) Spartan 04; Wavefunction, Inc.: Irvine, CA, 2003.

2a-AgPF6 Ag1-N1 Ag1-S1 Ag1-S2 Ag1-S3 Ag1-S2A Ag2-N2 Ag2-S4 Ag2-S5 Ag2-S6 Ag2-S5A

2.532(4) 2.6010(13) 2.7600(11) 2.6467(12) 2.5217(11)

N1-Ag1-S2A N2-Ag2-S5A Ag1-S2-Ag1A Ag2-S5-Ag2A

Ag1-N1 Ag1-S1 Ag1-S2 Ag1-S2A Ag1-S3 Ag1-S8 Ag2-N2 Ag2-S4 Ag2-S5 Ag2-S6 Ag2-S2 Ag3-N3 Ag3-S7 Ag3-S8 Ag3-S9 Ag3-S5

110.62(6)

144.56(5)

146.44(3)

2d-AgOTf

2e-AgOTf

2.538(4) 2.5777(14) 2.8205(14) 2.6416(14) 2.5197(13) 2.529(4) 2.6290(15) 2.8001(13) 2.5872(15) 2.5202(13) 112.158(10) 112.56(11) 144.64(5) 145.75(5)

2f-AgOTf

2.485(4) 2.6257(14) 2.7589(13)

2.529(5) 2.705(2) 2.7700(16) 2.4882(16) 2.5616(18)

2.5997(14) 2.4767(13) 2.553(4) 2.6065(14) 2.8501(13) 2.6033(14) 2.5121(12) 2.576(4) 2.6446(15) 2.8609(13) 2.5814(14) 2.5288(12)

106.76(8)

121.70(12) 120.78(10) 126.13(10) 131.39(10)

147.39(4)

127.60(7) 128.29(5) 131.29(5) 130.42(5)

2a-AgPF6 H3A‚‚‚benzene plane H4B‚‚‚benzene plane H5A‚‚‚benzene plane H6A‚‚‚benzene plane H6B‚‚‚benzene plane H21B‚‚‚benzene plane average

2c-AgOTf

2.526(2) 2.6374(9) 2.7973(8) 2.6035(9) 2.5357(8)

119.91(9)

2.524(3) 2.5805(15) 3.0096(10) 2.5280(10) 2.5554(10)

N1-Ag1-S2A N1-Ag1-S8 N2-Ag2-S2 N3-Ag3-S5 Ag1-S2-Ag1A Ag1-S2-Ag2 Ag2-S5-Ag3 Ag1-S8-Ag3

2b-AgOTf

2b-AgOTf

2.999

2c-AgOTf

2d-AgOTf

3.194 2.812

2.692

2.823 3.444 3.385

3.147 2.846

2.999

3.187 3.190

3.217

reaction of monoazatrithia-12-crown-4 (1)2 with the appropriate substituted benzenecarbaldehyde in the presence Inorganic Chemistry, Vol. 46, No. 16, 2007

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Habata et al.

Figure 1. ORTEP diagram of 2a-AgPF6 showing thermal ellipsoids at 50% probability. H atoms, the PF6 anion, and solvents are omitted.

of NaBH(OAc)3 in 1,2-dichloroethane under 1 MPa (argon atmosphere).

Figure 2. (a) Packing diagram of 2a-AgPF6 and (b) a partial magnified view. The PF6 anion and solvents are omitted. A schematic drawing of the zigzag polymer structure is shown in Figure 5.

The new ligands were treated with equimolar amounts of AgOTf or AgPF6 in CH3CN, CH3OH, or acetone to give silver triflate or silver hexafluorophosphate complexes in quantitative yields. We have reported that cold ESI-MS is a powerful tool in the determination of structures of silver triflate complexes with pyridylmethyl-armed monoaza-12-crown-4 ethers.8a In keeping with this, the structures of the silver complexes with 2a-2f in solution were examined by cold ESI-MS at 278 K. Intensities of normalized fragment ion peaks of the silver complexes with 2a-2f are summarized in Table 2. In the cold ESI-MS of the 2a-AgOTf and 2a-AgPF6 complexes, [42a + 4Ag + 3OTf]+ and [52a + 6Ag + 5PF6]+ were observed, respectively. Higher fragment ion peaks, [6(2b or 2c) + 6Ag + 5OTf]+ and [7(2b or 2c) + 7Ag + 6OTf]+, were observed in the 2b-AgOTf and 2c-AgOTf complexes. In addition, 2d-AgOTf, which has two F atoms on the aromatic ring, gave [52d + 5Ag + 4OTf]+. Therefore, the cold ESI-MS data suggested that 2a-2d would be more likely to form coordination polymers compared to a tetramer. On the other hand, 2e-AgOTf and 2f-AgOTf complexes showed only [3(2e or 2f) + 3Ag + 2A]+ as the highest fragment ion peaks. The results show that 2e and 2f would form, at maximum, a trimer. Ligands 2a-2e were treated with equimolar amounts of AgOTf or AgPF6 in appropriate solvents to give silver triflate or silver hexafluorophosphate complexes in quantitative yields. The structures of 2a-AgPF6, 2b-AgOTf, 2cAgOTf, 2d-AgOTf, 2e-AgOTf, and 2f-AgOTf complexes were determined by X-ray crystallography. Figure 1 shows (8) (a) Habata, Y.; Yamada, S.; Osaka, F. Inorg. Chem. 2006, 45, 987. (b) Habata, Y.; Osaka, F. Dalton Trans. 2006, 1836.

6532 Inorganic Chemistry, Vol. 46, No. 16, 2007

Figure 3. ORTEP diagram of the 2e-AgOTf complex with thermal ellipsoids at 50% probability. H atoms, OTf anions, and solvents are omitted. A schematic drawing of the cyclic trimer is shown in Figure 5.

the ORTEP diagram of the 2a-AgPF6 complex. In this complex, the Ag+ ion is five-coordinated by the ring N1, the ring S1, S2, and S3 atoms, and the S2A atom of the nearest-neighbor molecule. The Ag1-N1, Ag1-S1, Ag1S2, Ag1-S3, and Ag1-S2A distances are 2.532, 2.601, 2.760, 2.6467, and 2.5217 Å, respectively. Selected bond distances (Å) and angles (deg) are summarized in Table 3. As shown in the packing diagram (Figure 2a), 2a-AgPF6 forms a zigzag coordination polymer. Average distances between the H atoms (H3A and H5A) of the crown ring and the benzene plane of the nearest-neighbor molecule are about 2.85 Å (Figure 2b). It is well-known that the average

SilWer Complexes with Monoazatrithia-12-Crown-4 Ethers

Figure 4. Electrostatic potential isosurfaces (at 8.1 electrons/au3) of (a) 4-methoxytoluene, (b) p-xylene, (c) toluene, (d) 3,5-difluorotoluene, (e) 3,5dichlorotoluene, and (f) 4-nitrotoluene.

nonbonding CH‚‚‚π distance is estimated to be 2.91 Å.3a,9 Therefore, the CH‚‚‚benzene plane distances in the 2a-

AgPF6 complex are indicative of a CH‚‚‚π interaction. The silver complexes with 2b-2d are isomorphous. The CH‚‚‚ benzene plane distances of the other silver complexes are summarized in Table 2. On the other hand, 2e-AgOTf (Figure 3) and 2f-AgOTf complexes form a cyclic trimer, in which three azatrithiacrown rings are bridged by the S2, S5, and S8 atoms at position 7 of the crown rings. In these complexes, the Ag+ ion is five-coordinated by the ring N, three ring S atoms, and an S atom of the nearest-neighbor molecule. The average Ag-N, Ag-ring S, and Ag-bridged-S distances are 2.54, 2.67, and 2.51 Å, respectively. Kuppers et al. reported that a silver complex with trithia-9-crown-3 gives 2:1 and 3:3 (host-Ag+) complexes in a unit cell.10 The Ag-S distances in the 2e-AgOTf and 2f-AgOTf complexes are comparable with those of the 3:3 complex. In this system, the results of the X-ray data are consistent with the cold ESI-MS data, which reflect the structures in solution. The drastic structural change between the silver complexes with 2a-2d and those with 2e and 2f is explained by the substituent effect on the aromatic rings. To examine the

Figure 5. Postulated formation mechanism for coordination polymers and trimers. EDG ) electron-donating group; EWG ) electron-withdrawing group.

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Habata et al. electron density on the aromatic side arms, we calculated electrostatic potentials for model compounds. The electrostatic potential is a function describing the energy of interaction of a point positive charge with the nuclei and the fixed charge distribution of a molecule.11 The electrostatic potential isosurface shows the electron-rich region of the molecule. Figure 4 shows the electrostatic potential isosurfaces (at 8.1 electrons/au3) of substituted toluenes that were calculated by the DFT (B3LYP/6-31G*) method. As shown in Figure 4, 4-methoxytoluene, p-xylene, toluene, and 3,5difluorotoluene have electron-rich regions among the C atoms on the aromatic rings, while 3,5-dichlorotoluene and 4-nitrotoluene do not have electron-rich regions on the aromatic rings. Interestingly, the average CH‚‚‚benzene plane distances of the silver complexes with 2a-2e (Table 4) are lengthened with a decrease in the electron density on the aromatic rings (the CH‚‚‚benzene plane distance: 2a < 2b < 2c < 2d). Suezawa et al. reported an electronic substituent effect on intramolecular CH‚‚‚π interaction in 4-substituted aromatic compounds by nuclear overhauser enhancement (NOE) experiments.12 The order of the CH‚‚‚benzene plane distances in the silver complexes with 2a, 2b, 2c, and 2f that have (9) Madhavi, N. N. L.; Katz, A. K.; Carrell, H. L.; Nangia, A.; Desiraju, G. R. Chem. Commun. 1997, 1953. Grossel, M. C.; Cheetham, A. K.; Hope, D. A. O.; Weston, S. C. J. Org. Chem. 1993, 58, 6654. Takahasi, H.; Tsuboyama, S.; Umezawa, Y.; Honda, K.; Nishio, M. Tetrahedron 2000, 56, 6185. Evans, D. J.; Junk, P. C.; Smith, M. K. New J. Chem. 2002, 26, 1043. Guo, W.; Guo, F.; Xu, H.; Yuan, L.; Wang, Z.; Tong, J. J. Mol. Struct. 2005, 733, 143. Takemura, H.; Iwanaga, T.; Shinmyozu, T. Tetrahedron Lett. 2005, 46, 6687. Sako, K.; Mase, Y.; Kato, Y.; Iwanaga, T.; Shinmyozu, T.; Takemura, H.; Ito, M.; Sasaki, K.; Tatemitsu, H. Tetrahedron Lett. 2006, 47, 9151. (10) Kuppers, H.-J.; Wieghardt, K.; Tsay, Y.-H.; Kruger, C.; Nuber, B.; Weiss, J. Angew. Chem., Int. Ed. Engl. 1987, 26, 575. (11) Hehre, W. J. A Guide to Molecular Mechanics and Quantum Chemical Calculations; Wavefunction, Inc.: Irvine, CA, 2003; p 72. (12) Suezawa, H.; Hashimoto, T.; Tsuchinaga, K.; Yoshida, T.; Yuzuki, T.; Sakakibara, K.; Hirota, M.; Nishio, M. J. Chem. Soc., Perkin Trans. 2000, 2, 1243.

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4′-substituted aromatic rings is exactly the same as that of the NOE experiments. These results clearly suggest that the strength of the CH‚‚‚π interaction depends on the electron density on the aromatic rings. The cold ESI-MS, X-ray crystallography, and calculation of the electrostatic potential isosurfaces lead us to describe a formation mechanism for the coordination polymers and trimers (Figure 5). When the electron density on the aromatic side arm is relatively high, the CH‚‚‚π interaction may act so as to encourage the formation of the polymeric structures. On the other hand, when the electron density on the aromatic ring is low, the interaction is nonexistent, and the trimers form. In conclusion, we have demonstrated that the silver complexes with compounds 2a-2d bearing aromatic side arms with electron-donating groups and compounds 2e and 2f having aromatic side arms with electron-withdrawing groups form coordination polymers and trimers, respectively. These results indicate that the structures of silver complexes with monoazatrithia-12-crown-4 bearing substituted aromatic rings can be changed drastically by the strength of the CH‚ ‚‚π interactions, which are controlled by substituent effects on the aromatic side arms. Acknowledgment. This work was supported by a Grantin-Aid for Scientific Research (Grants 16550129 and 18550131) from the Ministry of Education, Culture, Sports, Science and Technology (Japan) for Y.H. Supporting Information Available: X-ray data of 2a-AgPF6, 2b-AgOTf, 2c-AgOTf, 2d-AgOTf, 2e-AgOTf, and 2f-AgOTf (CIF format) and cold ESI-MS data. This material is available free of charge via the Internet at http://pubs.acs.org. IC700538F